Chlorinated hydrocarbon compounds are often used as raw materials for preparing refrigerants, blowing agents, aerosol propellants, biocides and polymers. 1,1,2,3-tetrachloropropene is one of the main intermediates for preparing triallate, which is a chemical herbicide, and is also the main intermediate for the manufacture of 2,3,3,3-tetrafluoropropene, which is a new environmentally friendly refrigerant. One of the latest technologies for making 1,1,2,3-tetrachloropropene is dehydrochlorination of 1,1,1,2,3-pentachloropropane. One of the methods in the art for preparing 1,1,1,2,3-pentachloropropane is to use carbon tetrachloride and ethylene as raw materials to firstly prepare 1,1,1,3-tetrachloropropane, then conduct a dehydrochlorination to make 1,1,3-trichloropropene, and finally conduct an addition reaction with chlorine gas to prepare 1,1,1,2,3-pentachloropropane. This method of making 1,1,2,3-tetrachloropropene through four steps by using carbon tetrachloride and ethylene as raw materials is described in the following reaction equations:
U.S. Pat. No. 4,650,914 discloses a process for preparing 1,1,2,3-tetrachloropropene from carbon tetrachloride and ethylene where a concentrated aqueous solution of sodium hydroxide was used in the dehydrochlorination of 1,1,1,3-tetrachloropropane to prepare 1,1,3-trichloropropene, resulting in a large amount of waste water, and thus the entire process was not environmentally friendly. U.S. Pat. No. 8,907,147 and U.S. Pat. No. 8,993,816 disclose processes for preparing 1,1,2,3-tetrachloropropene where the dehydrochlorination of 1,1,1,3-tetrachloropropane to prepare 1,1,3-trichloropropene, was adopted via continuously charging 1,1,1,3-tetrachloropropane and continuously discharging 1,1,3-trichloropropene with rectification at 120° C. in the presence of ferric chloride, a Lewis acid catalyst. However, the control of polymerization side reactions was very difficult for the processes.
In the current state of the art, there are various side reactions such as polymerization and isomerization in the dehydrochlorination of polychlorinated hydrocarbons when a Lewis acid catalyst, such as anhydrous ferric chloride, is used. In particular, when 1,1,1,3-tetrachloropropane is dehydrochlorinated to make 1,1,3-trichloropropene (i.e. the step 2 in the above reaction sequence), dimerization, oligomerization, and/or polymerization occur extremely easily in the presence of a Lewis acid catalyst due to the presence of 1,1,3-trichloropropene. As a result, the reaction forms a lot of high boiling by-products, including carbonaceous materials such as coke, and turns black, and the catalyst is deactivated. Consequently, the yield of 1,1,1,2,3-pentachloropropane (i.e. the steps 2 and 3 in the above reaction sequence), which is the key intermediate of preparing 1,1,2,3-tetrachloropropene, is decreased, which further results in a decrease in the overall yield in preparing 1,1,2,3-tetrachloropropene.
In the art, in order to reduce the production of high boiling by-products, polymers or tar, U.S. Pat. No. 8,877,991 reduces the generation of high-boiling residues by adding water, however, the addition of water may cause corrosion in the production system. U.S. Pat. No. 8,889,927 reduces the generation of high-boiling residues by using the high-boiling materials produced in the previous step to inhibit the formation of dimers, oligomers and/or polymers. These high boiling materials generated in the previous step can deactivate the catalyst and complicate the reaction and purification system. U.S. Pat. No. 8,889,928 discloses the addition of a stabilizer or antioxidant to inhibit the production of dimers or polymers, however, the addition of a stabilizer or antioxidant increases the cost of production and waste treatment. U.S. Pat. No. 9,139,495 discloses a method which reduces the generation of high-boiling residues by adding carbon tetrachloride, however, carbon tetrachloride may destroy the ozone layer. The Montreal Protocol allows the use of carbon tetrachloride as a raw material but does not allow the use of carbon tetrachloride for other purposes, especially as a solvent or an additive.
Therefore, in the art, in order to increase the yield of 1,1,1,2,3-pentachloropropane and 1,1,2,3-tetrachloropropene, and to reduce the production cost, it is urgent to develop a manufacturing technology which is low-cost, easy to scale up and perform in commercial production, while having high selectivity and yield.